The invention relates generally to coal slurry fuel-injected combustion engines, and more particularly to coal-water slurry fuel supply and purge systems for compression ignition locomotive engines.
Conventional diesel engine fuel is a relatively low-grade, refined petroleum fuel oil which has desirable ignition and heat release characteristics. Diesel fuel oil typically has acceptably low levels of corrosive, abrasive and other noxious matter, and is generally in ample supply. However, it is known that other fuel mixtures, such as coal-water slurry fuel, may serve as an alternative lower cost fuel for compression ignition engines. Typically, coal slurry fuel may be in the form of either a dry powder or a liquid slurry which is generally a mixture of pulverized coal or other form of carbon dust in a liquid carrier such as oil or water.
The injection of coal-water slurry (hereinafter sometimes referred to as CWS) into an internal compression ignition engine, such as a large multi-cylindered diesel locomotive engine, poses problems not typically encountered in the injection of pure liquid fuels. An advantage of coal-water slurry is its low cost compared to higher grade petroleum fuels when petroleum prices become cost prohibitive. Consequently, significant development has been initiated to produce a vehicle capable of sufficiently utilizing CWS instead of conventional diesel fuel as an alternative fuel source. An article of general interest generally describing coal-fueled diesel engines for locomotives may be found in an article entitled "Coal-Fueled Diesel Engine Progress at GE Transportation Systems", authored by P.L. Flynn, B.D. Hsu and D.L. Leonard from the 13th Annual Energy-Sources Technology Conference and Exhibition held in New Orleans, La., Jan. 14-18, 1990, sponsored by the Internal Combustion Engine Division of the American Society of Mechanical Engineers. This article generally discloses a conceptual locomotive envisioned to utilize coal-water slurry but does not disclose a suitable fuel supply and purge system.
It has been predicted that significant fuel cost savings may result from the use of a coal-water slurry fuel in locomotive applications. However, a problem arises in integrating all of the systems into a working locomotive engine unit which can be operated in a railroad service. Normal CWS fuel supply systems are typically not suited for application in a locomotive engine given the amount of fuel required by a locomotive engine and the distance over which the fuel must be distributed throughout the engine. A problem arises since micronized coal particles mixed with water generally create a fuel which is difficult to store, pump and inject as compared with diesel fuel. Part of the reason is that the coal-water slurry tends to be unstable and to settle in tanks and fuel lines after a period of time, making it difficult to supply fuel to fuel injectors and distribute the fuel from the fuel tank throughout the operating cycle of the engine. Consequently, there exists a need to avoid long-term settling problems and to minimize losses throughout the fuel supply and distribution system.